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Assessing risks and vulnerabilities to climate change

2.2 Frameworks for assessing climate impacts, vulnerabilities and risks

Due to the complex nature of climate related risks with its interplay of hazard, exposure and vulnerability factors and the high uncertainty in data and process understanding, climate risks can barely be measured in a deterministic way. Instead, a risk assessment is in most cases a synthetic and agreed assessment based on a pool of information that consists of facts (e.g. climate observations, past events), simulations (e.g. climate projections, hydrological models), but also semi-quantitative or qualitative surveys, expert knowledge and narratives.

The methods adopted for risk assessments are often a combination of top-down assessments, which are usually based on quantitative data (e.g. census data, downscaled climate models) and use mapping and bottom-up methods, usually employing local knowledge in identifying risks and being rather qualitative in nature. Indicator-based risk assessments use sets of indicators that can be both quantitative and qualitative and can be assessed both through modelling or stakeholder consultation. For an overview on methods applied in Europe see EEA Report No 1/2018. The Urban Adaptation Support Tool describes the steps recommend for a CCIVA specifically for cities in more detail. However, the general approach is also applied for larger units such as districts or countries.

One framework to systematically conceptualize climate risks in line with the IPCC risk assessment concept are so called impact chains. Impact chains are cause-effect chains that illustrate all major factors and processes leading to a specific climate risk and assign these factors to the components hazard, vulnerability, and exposure. Impact chains are usually developed in a participatory manner together with stakeholders and experts. Impact chains help to better understand, systemize and prioritize the factors that drive climate impact related risks in a specific system of concern. Impact chains can foster the discussion on adaptation demand already in an early, qualitative stage of a risk assessment. For an operational risk assessment, impact chains can serve as a basis for the selection of appropriate methods such as models, indicators, review- or expert based assessment. Often, a combination of this methods is recommendable. For more information on impact chain based assessments see for instance the Risk Supplement to the Vulnerability Sourcebook.